125 carbs and reeds in a 115?

[cadman20]

I have a 1984 chrysler 115, I have a chance to get a set of 1985 Force 125 carbs and reeds, everything should bolt up, both motors use the same gaskets for the carb adapter plates.

Is there anything that will cause problems doing this? Jetting maybe?

Thanks in advance..

 

[eurolarva]

Re: 125 carbs and reeds in a 115?

Your 115 have two different carbs one is a WE 5 1 and the other is a WE52. Force 125 only calls out one carb 1300-803942T and the parts list calls for two of these. Carb repair kits for the 115 and 125 are also different. It may work but they are definitely different

 

[cadman20]

Re: 125 carbs and reeds in a 115?

Eurolarva,

Thanks for the reply, I understand what you are saying about both being completely different carbs.

Both the 115 and 125 have the same opening in the block that the reeds fit into, so the 125 carbs and reeds should bolt onto the 115 block.

I am just concerned about the 125 jetting and to much fuel to the engine.

I guess I am asking if anyone has used bigger carbs on their engine and what the results were?

 

[CharlieB]

Re: 125 carbs and reeds in a 115?

There is a number of engines that use different carbs for different levels of power.

You could check part catalogs to see if your 115 and the 125 have the same short block, which would tell you that the factory did use the carbs change to make more power.

Try it, remember to watch your max rpm as your prop may need a little more pitch if your power does increase.

 

[cadman20]

Re: 125 carbs and reeds in a 115?

CharlieB,

I checked both block numbers and they are the same. Good idea, Thanks.

 

[Frank Acampora]

Re: 125 carbs and reeds in a 115?

While the carbs are the same basic casting and will bolt right up, the reeds are exactly the same --they didn't change until later. You might squeek out a few more ponies by buying Boyeson reeds--some guys swear by them, but personally I don't like 'em.

If you bolt up the 125 carbs, they will work very nicely with no problems even though they may be jetted slightly differently. They are jetted and vented for the performance of the 125 but basically, at part throttle, your 115 is operating the same as the 125 and at full throttle, the carbs will compensate for the slightly less airflow and maintain mixture at 16 to 1 air to gasoline by weight. Actually, 16 to 1 is the best mixture for cruise but 14 to 1 is the power ratio and the jets LIMIT fuel flow at full throttle so you don't get richer than 14 to 1. At partial throttle, the high speed jet really does not function--the venturi, air bleed and low speed needles maintain a correct 16 to 1.

Where you WILL get into trouble is if you put leaner (smaller ) jets in the carbs. Unless you are compensating for altitude, this will cause the engine to run leaner than 14 to 1 at full throttle--say maybe 18 or 20 to 1. The lean mixture burns too hot and too fast causing detonation and melted pistons.

However, if you bolt on the 125 carbs, you will get a whopping 115 horsepower. These engines are not quite like auto engines where a higher flow carb--4 BBL versus 2 BBL will give an increase in horsepower. The 125 carbs have the same venturi size so you will basically get no increased airflow.

Horsepower on these engines is changed by adjusting bypass and exhaust port timing, and to a small degree, sometimes changing displacement.

Addendum: While the blocks have the same number, the 125 has a 2.875 stroke crank and the 115 has a 2.80 stroke crank. The ports on the 125 are raised about 1/16 inch to compensate for the longer stroke.

While it was still Chrysler, the long stroke 125 and 140 block was differentiated by a red or green paint swash on the bottom of the #4 cylinder casting. I don't know if Force continued the practice. The cranks have the same number and the only way to tell the difference is to measure them. I don't know how the factory kept them separate.